Apparatus for testing hydraulic and electric propeller governors



p 1949- R. D. MAYSTEAD APPARATUS FOR TESTING HYDRAULIC AND ELECTRIC PROPELLER GOVERNOR 7 Sheets-Sheet 3 Filed NOV. 14, 1944 v [NvENTOE a Ham/e0 L7. M4 YETEAD Haze/.9; Mic-H, fsme Air HIKE/5 a F4644 a): 7/: 52M

April 26, 1949. MAYSTEAD 2,468,635

APPARATUS FOR TESTING HYDRAULIC AND ELECTRIC PROPELLER GOVERNOR Filed Nov. 14, 1944 7 Sheets-Sheet 4 I N VEN 7'01? F/CHHEQ 0 Mn K! 7540 .By Ham/.5, K/scH, 5:57-51? 6: lime/.9

Foe THE Hem A 7'7'OR'NE Y5 April 26, 1949. R. D. MAYSTEAD 2,463,635

APPARATUS FOR TESTING HYDRAULIC AND ELECTRIC PROPELLER GOVERNOR Filed Nov. 14, 1944 7 Sheets-Sheet 5 RICHARD D. MHK? T540 HARE/a, K/spH, Fbs m? a: Haze/s For T EF/RM ATTOE/VEYF 5 6 0H .5 m t MJW; e 5 H 6 w x m0 a E F 2 a a m".v m e 7 7 MK MN N &

7 Mw-f mum R. D. MAYSTEAD APPARATUS FOR TESTING HYDRAULIC AND ELECTRIC PROPELLER GOVERNOR April 26, 1949.

' Filed Nov. 14, 1944 R. D. MAYSTEAD APPARATUS FOR TESTING HYDRAULIC AND A ril 26, 1949.

ELECTRIC PROPELLER GOVERNOR 7 Sheets-Sheet 7 Fil ed Nov. 14, 1944 p/ Q fl M M FO E THE FIRM Ame/v06 Patented Apr. 26, 1949 APPARATUS FOR TESTING HYDRAULIC AND ELECTRIC PROPELLER GOVERNORS Richard D. Maystcad, North Hollywood, Calif., assignor to Pacific Airrnotive Corporation, a corporation of California Application November 14, 1944, Serial No. 563,346

13 Claims.

My invention relates to testing apparatus and, more particularly, to a novel apparatus for testing propeller governors, both electric and hydraulic, such as are used in theautomati'c control of pitch of the blades of an airplane propeller,

Propeller governor-s can be classified under two general types, namely, hydraulic and electric. The hydraulic-type governor is driven by the airplane engine and includes fiyweights which actuate a pilot valve controlling the flow of engine oil to and from the hydraulic system of a propeller, which hydraulic system conventionally employs a double-acting piston movable along the axis of rotation of the propeller in response to differences in pressure on the inboard and outboard sides thereof, this piston being operatively connected to each of the blades of the propeller for simultaneous change in pitch upon movement oi the piston. The hydraulic-type governor includes a governor booster pump equipped with a suitable relief valve, and the pilot valve actuated by the 'fiyweights serves to control the how of the governorepressured oil to the hydraulic systern of the propeller and, in some instances, the drainage of oil from the propeller. The oil lines leading from the governor to the propeller pass through the rotating shaft on which the propeller is mounted, thus requiring sealing at the point of entry into or from the shaftby use of suitable s'o-called transfer rings which give rise to some leakage. In addition, provisionis often made .ior featheri and un'feathering the propeller blades, often by delivering oil at substantially higher pres-sure, derived from a separate pump and supplied to the governor through a governor transfer valve and a distributor valve associated with the shaft of the propeller to control the flow of highly-pressured oil in a manner to feather and unfeather the blades.

[.1 propeller governors, whether hydraulic or electric, serve the purpose of changing the pitch blades of the propeller in such way as to the speed of the propeller substantially l predetermined value, irrespective of changes engine output. In addition, most governors provide means for changing the speed at which the propeller is governed, for example changing the setting of a spring resisting outward movement of the governor flyweights by centrifugal force. In hydraulic-type governors, the setting of this spring adjustment is controlled either by meclanical means or by the so-called electric head. In either instance, the speed at which the system governed is under the control of the pilot or flight engineer. Stated generally, the

pilot sets this adjustment for the desired engine speed. If the governor is maintaining engine speed at this value, the condition is said to be on-speed. If the speed of the engine is higher or lower than that called for by the governor, the condition is said to be 'o-verspeed or underspeed, respectively.

Hydraulimtype propeller governors now in use are in four differently operating types. The first class is known as the controllable governor. When in underspeed condition, high-pressure oil enters the propeller line to decrease the pitch, while overs-peed condition permits oil to drain from the propeller line to increase the pitch. In an onspeed condition, the pilot valve closes the propeller line to entrap the oil therein and maintain the pitch. A second widely used type is known as the Hydromatic governor, which may be of the single-capacity or double-capacity type, the latter being very widely used on commercial and military aircraft. In the Hydromatic governor, an underspeed condition per- 'mits oil to drain from the propeller to decrease the pitch; an overspeed condition permits highpressure oil to enter the propeller to increase the pitch; and an onspeed condition permits the pilot valve to close the propeller lines to maintain the pitch. Hydromatic governor is feathered by oil delivered from an auxiliary source to the propeller. The third type is known as the accumulator-type governor and differs from the Hydrornatic governor primarily in employing accumulator which, during normal propeller operation, becomes charged with pressured oil, stored oil being forced to the propeller system during periods when other oil is not available. The fourth relatively new type is known as the "double-acting governor. When in underspeed condition, the inboard side of the propeller piston drains and high-pressure oil is supplied to the outboard side, thus decreasing the pitch. In an ovcrspeed condition, the outboard side of the propeller piston drains while high-pressure oil is supplied to the inboard side to increase the pitch. In an onspeed condition, the governor pilot valve closes the propeller lines to maintain the pitch. lieathering is obtained by supplying oil from an auxiliary source to the propeller.

On the other hand, electric-type propellers prov'ide a reversible electric motor associated with the propeller for changing the pitch of the blades. The direction and degree of forward or rearward motion is controlled by a single-pole, doublethrow switch in the propeller governor which in turn is actuated by movement of the governor flyweights. Certain auxiliary mechanism and electrical connections are also provided.

It is an object of the present invention to provide a testing apparatus for various types of propeller governors. From the above, it will be apparent that the various governors operate differently and require somewhat different test procedures. I-Ieretofore there has been no universally applicabie testing apparatus, and the hydraulic, electrical, and variable-speed drive arrangement of the present invention are believed to be fundamentally new.

A proper testing of any propeller governor makes desirable the simulation of conditions during actual use, e. g., in flight, and it is an object of the present invention to provide a testing apparatus which will simulate governor performance in such use and which will, for example, maintain and control pressures, temperatures, and viscosity of the oil to be similar to those encountered during actual use of the governor.

It is another object of the invention to provide a testing apparatus having elements substantially duplicating the action of engine, propeller, and aiiiliated parts, and in which the propeller governor itself can be made to control such elements. Many difficulties are encountered in this connection as it is impractical to conduct governor tests during flight or while the governor is actually connected to and driven by the engine.

Further, it is impractical to attach the governor to a test engine and propeller as, even then, actual flight conditions cannot be duplicated.

In the present invention, a variable-speed drive is employed to simulate the engine. It is an object of the present invention to operate this drive under the control of the propeller undergoing test. In testing a hydraulic governor, this makes desirable employment of a hydraulic actuator simulating the action of the hydraulic system of the propeller, and the invention includes among its objects the use of such an actuator hydraulically associated with the governor under test and the operative connection of the actuator to vary the speed of the drive unit. For 1 example, the hydraulic actuator may comprise a hydraulic cylinder controlled by the governor output and, in turn, controlling the speed of an electric drive unit, to the end that underspeed, onspeed, and overspeed conditions can be simulated.

Another object of the invention is to provide a governor testing apparatus including a substantially-constant-speed electric motor connected to drive the governor through a variablespeed transmission, the speed being determined by the movement of a control member, and to operatively connect this control member with the overnor under test. Movement of the control member is preferably by use of a reversible pilot motor. In testing an electric governor, the circuits of the pilot motor can be energized through relays controlled by the electrical contacts in the governor itself. In testing hydraulic governors, a hydraulic control means controlled by governor output can be used, together with means for translating movement of the hydraulic control means into electric variations which actuate the pilot iotor. In the preferred embodiment, this hydraulic control means includes the hydraulic actuator and an automatic control unit. It is an object of the invention to provide such systems; to provide a novel hydraulic control means; to provide a novel automatic control unit for translating movements of a hydraulic actuator into electric variations; and to provide the entire system with means to accommodate the different types of governors being tested.

Other objects of the invention lie in the provision of a novel test stand for the testing of propeller governors; a novel electrical system for energizing the governor or its accessories undergoing test and for indicating overspeed, underspeed, and onspeed conditions; a novel hydraulic system for testing any one of a number of different types of governers; novel means for controlling the temperature of the oil used for test purposes in its flow through a closed system incorporated in the test stand; and to provide a novel arrangement of electrical and hydraulic meters for indicating flow rates and pressures. Further, the invention has among its objects the provision of a self-contained test stand which can be con nected to existing electrical outlets and, if desired, to existing water lines for testing one or a number of different types of propeller governors.

Other objects and advantages of the invention will be evident to those skilled in the art from the following exemplary description of an embodiment which has been found to be particularly useful in the universal testing of propeller governors.

Referring to the drawings:

Figure 1 is a front view of the test stand with the front wall and a portion of the control panel broken away;

Figure 2 is a face view of the control panel;

Figure 3 is a sectional view at one end of the test stand, taken substantially along the line 33 of Figure 1;

Figure 4 is a sectional view at the other end of the test stand, taken substantially along the line 4-4 of Figure 1;

Figure 5 is a vertical sectional view through the automatic control means of the invention, taken substantially as indicated by the line 55 of Figure 3;

Figure 6 is a sectional view, taken along the broken line 6-5 of Figure 5;

Figure 7 is a vertical sectional view, taken along the line !-1 of Figure 5, showing one set of control elements in elevation;

Figure 8 is an enlarged fragmentary view, taken similar to Figure 7 but showing the set of control elements in section;

Figure 9 is a vertical sectional View of the governor mounting pad and the drive connection for the governor, taken substantially along the line 99 of Figure 3;

Figure 10 is a view similar to Figure 6, showing the connection between the automatic control unit and the hydraulic actuator;

Figure 11 is a pipeline diagram illustrating the hydraulic system;

Figure 12 is a wiring diagram of the test stand;

Figure 13 is a view diagrammatically illustrating the elements employed in a typical hydraulically operated system for controlling the pitch of a propeller; and

Figure 1c is a view diagrammatically illustrating the hydraulically operated propeller governor shown in Figure 13, in this instance a Hydromatic double-capacity governor, in an onspeed condition.

Typical hydraulic governor and operation A complete understanding of the invention requires knowledge of the operation of the various governors to be tested. As exemplary, Figures 13 a e -cs and 14 show atypical widely-used hydraulic-governor, namely, the Hydroroatic double-capacity :governor and its hydraulic and mechanical environment, the governor setting in this instance being manual. It will "be understood that these views are merely diagrammatic and are presented merely as an aid in "understanding the test operations 'to be .later described.

In Figure 13, one of several propeller blades is indicated by the numeral 20. Each blade has a crown gear 2| meshing with a gear '22 of a cam .23 disposed in the forward part of the propeller and rotatable about the axis of an engine-driven shaft the engine housing being indicated at 25. Thecam 23 provides one or m01-e cam slots ZLone ofthese being shown as including an operating portion 28 and a feathering portion '29. In each cam slot is a roller 30 which is moved forwardly and rearwardly by a piston 3| sliding in a domed cylinder 32. The outboard side of the piston Ill bounds an outboard chamber 33 and oil can flow to and from this chamber through a pipe M. Similarly, the inboard side of the piston 5i bounos an inboard chamber 35 to and from which. oil may flow through a pipe 36 under the control of propeller governor indicated generally by the numeral All.

Within the propeller shaft is a propeller distributor valve, indicated generally by the numeral 4!, which need not be described in detail as it is well known in the art. Suflice it to say that this distributor valve includes a hydraulically actuated valve member l3 sliding in a ported-cylinder and normally in the position suggested in Figure 13 to supply oil from a main engine pump '45 through pipe all and passage 4'! to the pipe whereby the outboard chamber -33 tends to receive oil at a pressure determined by the engine pump this oil pressure tending to move the piston. ill inwardlyto decrease the pitch of the propeller blades. The blades themselves have centrifugal moments (tending normally 'to turn he blade toward low pitch) exceeding their aerodynamic moments (tending to move the blade toward high pitch), the net moment aiding engine-pressured oil in the outboard chamher 33 in moving the blades toward low pitch position. To move the blades toward high pitch position, engine oil augmented pressure is de- 'livered by the governor at to passageway '48, annular space 49, and 5! the distributor valve positioned as shown transferring this governor-pressured oil through. the pipe to the inboard chamber is pr ssuredoil is transway Ml to the annular space 29 by use of transfer rings 5!.

The governor Ml illustrated in Figure l4l'wi-t-h flyv/eights 52 in onspeed condition. These flyweights are pivoted at to a structure, not shown because of the diagrammatic nature of Figure 14;, which s driven by the through splined connection M Figure 13. The poo. determines the vertical n V. 55, shown in onspeed position and having a land 55 closing off El and 58 in this position but providing immediately above the land 5%.

A governor oil pump 5!! intakes from a passage 6| communicating through a pipe 52 with the main engine pump High-pressure oil from the governor pump is delivered to a passage 63, and a spring-loaded pressure relief valve 65 controls the maximum pressure in the passage 63 by moving leftward to bypass oil from the of the fiyvveigh'ts '52 ot valve passage "63 to the passage Bl. The passage 51 communicates with the rear of the pressure relief valve 65, as shown.

When the governor is operating in an overspeed condition, the flyweights 52 move outward as indicated by the full-line arrows to raise the pilot valve 55, thus delivering pressured oil from the passage 63 to the passage 53 and thence through passageway 48 and the distributor valve =44 'to'the inboard chamber 35 to move the piston .3! outward in .manner to increase the pitch. Oil from the outboard chamber 33 drains through the distributor valve 41 and. returns to the dis charge of the main engine pump it through the pipe 46.

When. the governor is operating an undersp'eed condition, the flyweights move inward as indicated by the dotted arrows, thus lowering the pilot valve The inboard chamber 35 then chains 'to the engine housing through the distributor valve rll, passageway passage 58, and through the interior vertical passage of the pilot valve Eli. In the onspeed condition illustrated in Figure i l, the land 5t of the pilot valve locks the liquid in the hydraulic passages leading to the chamber 35.

The speed setting of the governor is adjusted by turning a pulley '5"! to turn a pinion 58 meshing with a rack assembly 69, and thus changing the tension of a'speeder spring it urging the pilot valve 55 resiliently downward, aided by a counterbalance spring lilo, The low speed setting of the governo adjusted by changing the vertical position of a stop ll associated with the rack, assemloly while the high speed setting of the governor is changed by varying the adjustment of a screw bearing against a pin set one of a plinality of openings of the pulley El, this type of adiusting means being commonly known and th fore not herein shown or described in detail.

in feathering the propeller, high-pressure oil from l, auxiliary pump is delivered through a flexible hose to a high-pressure port 73. The pressure several hundred pounds per square inch and substantially higher than the pressure output of the pump to so as to displace a springloaded high-pressure valve l' i leftward to close off the upper portion of the passage lit and open the lower portion to the high-pressure oil. The hydraulic pressure is insufii'cient to actuate the distributor valve Lll but enters the inboard chamber Clo to displace the cam roller into the feathering portion 23 of the cam slot ill to .move the blades into feathered position. To unfeather the propeller, a pressure even higher than that used for feathering is supplied to the highpressure port lll a pressure sufficiently high to actuate the distributor valve in such way as to connect the high-pressure fluid to the outboard chamber to connect the inboard chamber 35* to the discharge off the main engine pump 45. The high-pressure fluid from the auxiliary source is usually under the control of a pressure cutout switch mounted on the governor, but not shown.

General arrangement of intention Generally speaking, the invention includes a test stand is, best shown in Figures 1, 3, and 4, approximately one-half of the top forming a deck 'l't and the balance providing a sloping panel 11, suitable internal. framework being provided and the test stand being provided with casters 18. Governor mounting means 19 extends to or through the deck '16 to mount the governor 40 undergoing test.

A variable-speed drive means is provided, including an electric motor 39 and a variable-speed transmission at controlled by a pilot motor which, in turn, is actuated forwardly or rear wardly by an automatic control unit best shown in Figures 3 and 5 to 8. A hydraulic actuator 84, connected hydraulically with the governor 4d and controlled thereby, is operatively connected to the automatic control unit 83, and is shown in Figures 1, 3, and 10.

As best shown in Figure 1, the inteior of the cabinet of the test stand is provided with a shelf 86 on which positioned some of the electrical equipment. Below this shelf is an oil reservoir 8? provided with an electric heating unit 83 and a cooling unit 89, preferably a pipe coil submerged in the oil and equipped with a solenoidoperated valve 5-] controlling the flow of cooling water from a connection 9! through the coil and to waste through a connection 92. The heating unit 83 and the cooling unit 89 are controlled in a manner to be hereinafter described so as to maintain the temperature of the oil between narrow limits.

Oil from the reservoir 81 moves through two filters 83 and, respectively, to a low-pressure pump 94 and a high-pressure pump S5 (Figure l) simultaneously driven by an electric motor 96. From here, the oil is delivered through pipes, valves, meters, etc., to the governor and, in some instances, from the governor to the hydraulic actuator as, the oil being returned to the reservoir 8? for temperature adjustment and for reuse.

The general arrangement is such that the control panel ll, with its various valves, gauges push buttons, and operating controls, is within easy reach and in full view of the operator. governor under test may be operated with the left hand. while leaving the right hand free to operate the controls on the instrument panel. The interrelation of the various generally described elements and the function of the various controls and indicating means on the sloping panel I! will be made evident hereinafter.

Governor mounting and drive means The governor mounting means I9 is best shown in Figure 9 as including a plurality of slotted clamps 9'2 engaged by nuts threaded to slottraversi g studs 83 spaced peripherally around the base of the governor and engaging a lower flange thereof. This type of clamping means permits quick attachment and detachment of the governor to a governor mounting pad 5 To aid in proper location of the governor, a plurality of dowels extend upward from the pad into correspondingly-spaced openings of the governor. The pad I Gil provides a chamber SE72 for receiving the splined connection 53a of the governor. Surrounding the pad W0 is a suitable sump member I63 to receive any oil leakage incidental to the attachment or detachment of the governor. A mounting pad ring IM- is connected below the pad I03 by countersunk screws I95, and a tubular m mber I535 is welded to the ring I04 and to a plate l0? secured to the upper end of the variable-speed transmission 8!.

The pad the and the ring I 34 provide several pad passages registering with the fluid passages of various hydraulic governors, these pad passages being shown both in Figure 9 and in Figure 11. They include a governor-pump intake Lil passage IIO fed by a low-pressure line III which, with the Hydrornatic governor previously described, corresponds to the pipe 62; an inboard output passage II2 communicating with a pipe i 3; and an outboard output passage II4, used only when testing the double-acting type of governor and communicating with a pipe II5. In addition, the chamber I02 receives the discharge and leakage from the governor and communicates through a passage IIB with a pipe III. The pad I00 also provides a connection H8 for receiving a rubber hose IIS connected to the high-pressure or feathering port of the governor, e. g., the port I3 previously mentioned.

The variable-speed transmission BI provides an upwardly-extending output shaft I20 connected by a flexible coupling I2I to a stub shaft I22 carrying a drive connection 23 meshing with the splined connection 53a. Surrounding the coupling !2I is a gear I24 meshing with a gear 525 to drive a tachometer connection I26 which extends to a tachometer I21 mounted on the control panel (see Figure 2) and to a revolution counter I28, also mounted on the control panel. The tachometer I21, the counter I28, and a timer I29 are a part of a standard chronotachometer operating substantially as follows. The tachometer I21 gives a reading of the instantaneous speed of the drive connection I23 at any time. The counter I28 records the total number of revolutions from the time that start button 30 is depressed, this counter being resettable to zero by a counter reset knob I3I. Pressing of the button I30 also starts the timer I23 and both can be simultaneously stopped by releasing the start button I30 to give integrated readings of total revolutions and time which, if divided, gives a more accurate indication of speed than does the tachometer I21. The timer I29 provides a timer reset I32 for returning the timer to zero. This chrono-taehometer system provides also for the automatic stopping of the timer I29 after the lapse of a predetermined period of time. Thus, a toggle switch I33 may be thrown to automatic position to accomplish this result. This chrono-tachometer is not, per se, a part of the present invention and its operation will be understood by those skilled in the art.

While various means may be employed for changing the speed of the governor drive connection 53a, the variable-speed transmission 8|, driven by the substantially constant-speed motor 80, has been found excellently suited to this purpose and very rugged and dependable in operation. The variable-speed transmission 8| may be of the V-belt type, including separable cones I34 driven by the motor 86 and separable cones 535 driving the output shaft I20, the two pairs of cones being connected by a V-belt I36. A control member in the form of a control shaft I31 serves, when rotated in one direction, to increase the speed and, in the other direction, to decrease the speed of the output shaft I20 by relatedly changing the effective diameters of the pulleys formed by the cones I34 and I35. Such variable-speed transmissions, with a suitable hand wheel connected to the control shaft I31, are well known and need not be further described. They are readily adapted to the invention by removing the hand wheel and rotating the control shaft I3I forwardly and rearwardly by use of the pilot motor 82, which is of the reversible type. The connection between the pilot motor 82 and the control shaft I3! is best shown in Figures-; 6, and 7 and should preferably' be a gear reduction drive.

I38 meshing with a worm gear I38 secured to the control'shaft I31, thisgearing beingmounted.

in" a gear box I40 depending from a sub-housing I4I of the variable-speed transmission 8|. While the pilot motor 82-inay be of any suitable revers ible' type, the connections hereinafter described employ a small three pha-se reversible. motor in this connection. A gear reduction in the neigh 'borhood' of 100:1 will usually befound satisfactory but will vary with the variable-speed transmis'sionBI employed.

Automatic control means The automatic control means, comprising the automatic control unit 83 and the hydraulic actuator 84, serves thefunction of' increasing and decreasing the speed of the governor in response, respectively to underspeedand overspeed conditions-inthe governor. In effect, the automatic control unit 83 and the hydraulic actuator 84 simulate the operation of a hydraulically-controlled propeller, while the motor 88 andvariablespeed transmission BI. simulate; the airplane engine. Thus, the hydraulic actuator receives oil.

under the control of the governor and, in turn, controls the automatic control unit 83 to control the direction and time of rotation of the pilot motor 82 in such manner as toadjust the speed of the drive connection. 53a to bring the governor to an onspeed condition.

The automatic control unit 83 includes a top wall I43, abottom Wall I44, and a plurality of side Walls 545; A shaft I46 is connected to the worm gear I39 to rotate with the control shaft I 31. This-shaft I46. is journalled in bearings in the upper and lower walls I43 and I44, as is also a similar shaft I41 (Figure 6). These shafts are interconnected by gears I48 and I49 to turn in opposite directions with the same degree of angular movement as the control shaft I31, the gears being respectively attached to the shafts. In ef-- fect, theshaft I46. and its associated equipment control the pilot motor 82 when testing one type of hydraulic governor, e. g., the Hydromatic type, while the shaft I41 and its associated equip ment control the pilot motor 82 when testing another type of hydraulicgovernor, e. g, the controllable governor. As previously mentioned, the hydraulic relationships of these two overnors are opposed, and compensation for this is provided by the opposite rotation of the shafts I46 and I41. As the equipment associated with each of these shafts is identical in construction, detailed description of one will suffice. Figure 8 best indicates the equipment associated with the shaft I46 and corresponding equipment associated with the shaft I41 will be indicated by primed, but otherwise corresponding, numerals.

Referring particularly to Figures 5, '1, and 8, the shaft I 46 is surrounded by two sets of control elements; The upper control element or drum is indicated generally by the numeral I56 and includes two disks I5I formed of insulating material, each providing a central opening I52 of such size as to journal freely on the shaft I45. A contact ring I53 is clamped between the disks I5I and provides a central opening larger than the shaft I46 to avoid electrical contact therewith. The periphery of the contact ring I53 is engaged by a brush contact I54 mounted on, but insulated from, the adjacent side wall I45. The disks I'5I are clamped against the ring I53 by a For ex-" ample, the pilot motor 82 may carry a warm plurality of bolts I55, at least one of which carries a contact member I56 extending downwardly,

tact rings Itl and Hit are spaced from the shaft.

periphery. A bolt i634 is electrically connected to the contact ring I 6! and extends upwardly to retain a contact member I65 in position. Simi larly, oneor more bolts I61 are electrically con nected to the contact ring I62 and pass upward.

through enlarged openings of the contact ring I6I to be insulated therefrom, the upper end of the bolt I61 supporting, and being electrically connected to, a. contact member I68. The contact members 165 and I63 provide relatively rigid upturned portions carryin contact means hereinafter referredv to as side contacts I69 and I10, or as: decrease and increase contacts I 69 and I16, respectively. These side contacts are dis-'- posed in the same horizontal plane as the-inter-- mediate-contact I5! and are spaced apart a sufficient distance to accommodate the intermediate contact I5'i, while permitting at least several degrees of rotation before the intermediate con* tact, if centrally disposed, will electrically engage either of the side contacts I69 or I10. The peripheries of the contact rings ISI and I62 are engaged, respectively, by brush contacts HI and I12 mounted on, but insulated from, the adjacent side wall I45. Correspondingly, current can be conducted from the brush contact I1I to the 4 side contact I69 and from the brush contact I12 to the side contact I10.

Secured to the lowermost disk I5I' by screws I13 is a pinion I14 which rests frictionally on a flange of a sleeve bearing I15 in the lower wall I44 and which journals the shaft I46. The pinion I14 journals freely on the shaft I46 but definitely controls the angular position of the lower drum I60 and the corresponding side contacts I69 and I16; Immediately above the uppermost disk I5I ofthe lower drum I66 is a collar I16 rigidly connected to the shaft I46, as by a set screw I11. The lower drum I66 is free to rotate on the shaft I46 between the flange of the bearin I15 and the collar I16. A helical spring I18 is compressed between the collar I16 and the lower disk I5l of the upper drum and serves the important function of urging this drum resiliently upward into frictional contact with a surface I19 of the gear M8.

The pinions I14 and I14 (the latter being associated with the shaft I41 and shown in Figure 6:) are both meshed with a gear I secured to a third or oscillating shaft I8I journalled in bearings in the upper and lower walls I43 and I44. The shaft I8I oscillates in response to movement of the hydraulic actuator 84 to rotate the lower drums I68 and I60 in opposite directions, these d ru'ms freely journalling respectively on their shafts I46 and I41 during this opposed movement.

The interconnection between the oscillating shaft I8I and the hydraulic actuator 84 is best shown in Figures 3 and 10, particularly the latter. The preferred connection includes an arm I85 fixed to the lower end of the oscillating shaft I85 and providing a slot I80. A pivot pin I81 may be moved along this slot I85 and clamped at various positions therealong by means of a nut i823 to provide an adjustment varying the lever arm of the arm I85. Overlying the arm I85 is an attachment member l90 providing bifurcations extending on opposite sides of the pin to leave a U-shaped slot l9! in which the pin extends and in which the pin may move slightly as the arm I swings. The attachment member I99 is adjustably connected to a bar I93 to permit angular adjustment therebetween about a bolt l94 traversing both the member and the bar. The attachment member I provides an arcuate slot I95. A bolt I96 is adjustably positioned in this slot and extends upward through an opening in the bar I93 to carry a spring I91 adjustably compressed against the top of the bar I93 by the bolt. This provides an adjustable frictional connection between the bar I93 and the attachment member I90.

The hydraulic actuator 84 comprises essentially a piston-cylinder arrangement simulating the arrangement in the forward end of the propeller, e. g., the elements 3I, 32 of Figure 13. This cylinder-piston arrangement should be doubleacting and may comprise two cylinders with interconnected pistons. However, the simplest embodiment includes a double-acting piston 200 movable in a cylinder 20I to define a low-pressure or outboard chamber 202 at one end of the piston communicating with pipes 203 and 204, and a high-pressure or inboard chamber 205 at the other end of the piston communicating with a pipe 205. 200 with the bar I93. This is desirably accomplished by threading a nut 208 on this piston rod and held in place by a lock nut 209. The bar I93 is welded to the nut 208. By disconnecting the bolts 94 and I96, the bar can be adjusted longitudinally of the piston rod 201 by turning of the nut 203, after which the lock nut 209 is employed to rigidify the attachment.

Hydraulic system Referring particularly to Figure 11, temperature-controlled oil of proper viscosity is drawn from the reservoir 81 through the two filters 93 by the low-pressure pump 94 and the high-pressure pump 95 simultaneously driven by motor 96. The low-pressure pump 94 discharges to a pressure regulator, shown as comprising a pressure relief valve 255 which by-passes oil to reservoirreturn pipe 215 in such amount as to maximize the pressure in the low-pressure line III leading to the governor-pump intake passage IEO of the governor mounting pad I00. The pressure relief valve 215 is usually set to simulate pressures derived from the engine oil pump 45, e. g., at about 50 lbs/sq. in, A low-pressure gauge 2I8 registers the pressure in low-pressure line III immediately beyond a valve H9 in this line. The pipe 203 leading to the outboard chamber 202 of the hydraulic actuator 84 joins the low-pressure line IIl ahead of the valve 2I9 and includes a valve 220.

The high-pressure pump 95 discharges to a pressure regulator, shown as a pressure relief valve 222, which maximizes pressure in highpressure line 223 by by-passing oil to the reservoir-return pipe 2I6. The high-pressure system simulates the action of the auxiliary pump used for feathering purposes and serves other functions to be later described. Ordinarily, the pressure relie. valve 222 is set to maintain the dis- A piston rod 201 connects the piston :3

charge pressure at about 750 lbs/sq. in. Another reservoir-return pipe 225 is connected to the highpressure line 223 through a valve 226. The highpressure line 223 may also be connected to the low-pressure line III beyond the valve 2I9 by opening a valve 221. A valve 228 is also disposed in the high-pressure line 223 to control the delivery of high-pressure oil to the connection II8 and hose I I9 for feathering purposes, the feathering pressure being indicated on a high-pressure gauge 230.

The low-pressure oil entering the governor through the low-pressure line II I is pressured by the governor pump 60 and discharged, under the control of the flyweight-operated pilot valve 55, through the pipe I I3. This pipe includes a valve 232 and delivers the governor-pump-pressured oil to a pressure relief valve 233 which maximizes the pressure in the pipe 205 leading to the inboard chamber 205 or the hydraulic actuator 84. The pressure relief valve 233 is set to relieve excessive pressures by discharging into the reservoir-return pipe 225, the setting of this valve 233 being above the normal output pressure of the governor pump, e. g., at about lbs/sq. this valve thus being normally closed during automatic operation of the system.

The pressure of the oil discharged from the governor is indicated on a pressure gauge 235 communicating with a pipe 236 which opens on the pipe II3 ahead of the valve 232 and which contains a valve 231. The pipe 206 is primarily a pressure line, transmitting the governor-pump pressure to the hydraulic actuator 84, the main stream of oil discharged from the governor pump flowing through the pipe 236, in which the pressure is maximized by a pressure relief valve 239, and thence to an integrating-type flow meter 240 before being returned to the reservoir 81. The flow meter 240 indicates the total flow and drives a small generator, not shown, which delivers to a meter 24I on the control panel a potential which is a function of the rate of flow, whereby this meter can be calibrated in terms of quarts per minute. A switch button 24Ia operates a switch delivering this potential to the meter 24I so that pressing of this button gives a reading of instantaneous flow rate. If for any reason the pressure on the pipe 236 exceeds the setting of the pressure relief valve 238 (which is usually set at about 200 lbs/sq. in.), the excess pressure is relieved into the lefthand end of reservoirreturn pipe 225.

To simulate transfer ring leakage when testing or setting the governor for high or low R. P. M., a small pipe 242 extends from the pipe I 53 to the pipe 236 and includes a small fixed-sized, sharpedged orifice 243 of a diameter of about .031 inch so as to substantially duplicate the normal transfer ring leakage of about 1 quart/min. Flow through th pipe 242 is controlled by a manual valve 244 and return flow is prevented by a check valve 245. The pressure in the pipe 242 ahead of the valve 244 corresponds to the pressure in the pipe II3 beyond the valve 232.

The internal leakage from the governor discharges into the chamber I02 of the governor mounting pad I00 and through the pipe II! to a flow meter 250 discharging through a pipe 25I to the reservoir 81. This flow meter 250 is positioned behind a hinged door 25Ia on the front of the test stand (see Figure 4). It is preferably of the type including a graduated glass cylinder 252 conducting the oil stream. In this oil is submerged a float 253 which has a density greater l3 than-that of the oil;- thus tending todrop in the cylinder 252, butwhich iscarried upward by the rising oil to a position which is a'function of the rate: of new orthe oil in the pipe.

For the purpose of testing the double-acting governor, pipe i it, communicating with the out-' board outputpassage H t of the pad I00, extends to apressure gauge 2'55 and thence through a manually-operated valve 256 to a pressure relief valve 251 The pressure in the pipe H5 is nor-' mally transmitted through th pipe 204 to the pipe 203- and the outboard chamber 202 of the hydraulic actuator 34, but the pressure relief va'lve zlil relieves excess pressures to the pipe 258 joining the reservoir-return pipe 2225. Themessure relief valve is normally set at about 100 lb'sE/s'q; I in.

Electrical system The-electrical system is energized'from'a threephase line 270, the test stand providing a receptacle 21'! (Figure 3) into which such a line can be" plugged. Linevoltage is conventionally 230 volts. A master control contacter 252' energizes and"deenergizes the entireelectrical system. This contacter may be of any ofth'e well-known solenoid operated, so-calld magnetic contacters eluding conventional" thermal overload means 214 in the holding circuit and including start button Z'Hiand a stop button 216' which, when depressed, respectively close and open the contacts of the contacter' .212 to energize and deenergize the entire electrical system.

A drivemo'tor contacter' 200 is connected by conductors 23!, 282; and 283 with the master con-' 5 trol contactcr 212' and controls the forward or reverse operation of the motor at; which is of the three-phase reversible type, to provide for the testing of right'-handrotation or left-handrotation governors. The drive motor contacter 280 may be of any well known type capable of stopping and starting the motor 39} and controlling its direction of rotation. Assnggested in- Figure 12', it includes conventional thermal overload means'ZiB-i in'the holding circuit and includes a'stopbutton 235, a forward button 2%, and a reverse button 281. g the" forward button 286, the motor 80 is phased to' operate in a forward direction until the stopb'litt'on 285' is pressedi By momentarily closing the reverse button .281, the motor is phased to operate in a reverse direction.

A pump motor cont'acter 2%, similar to the master control contac'ter 212, is respectively conne'ctedto' conductors'28l, 282, and 2B3 to control the en'ergization'of the pump motor 96 which is of the three-phase'type. It provides a-start button 292" anda stop button 293 for controlling the operation of the pump motor;

The pilot motor 82 may be any desired reversible-type electric motor. A three-phasemotor is illustrated, with one supply conductor 295 joined with the conductor 28'! and the other supply conductors 2536 and 29'! extending to increase and decrease relays 3st and 30"! and thence to conductors 302 andlflt" joining conductors 282 and 283; respectively. Included in the circuit provided by conductors 302 and 303 is a relay 305 which closes only when the main motor 80 is operating in either a forward or reverse direction,

this being accomplished" by connecting a solenoid 306' across the drive motor contacter 286 to be energized by one of the three phases when the contacter is closed, e: g, by use of conductors 30'1a'nd'308, asshown.

By momentarily pressing The increase relay 300 includes a's'o1enoid 3'l0 operating two single-pole;-do'uble-throw switches having b1ades 3l I- and- 312 normally'respe'cti-vely' engaging upper contacts but movable" upon en'- ergization of the solenoid 3I0 to engage their respective lower contacts; Similarly, the decrease relay 30-lincludes a solenoid 315 opera tively connected to two single-pole, double-throw switches having blades 3l6 and 3H normally engaging their upper contacts but movable to engage their lower contacts upon energization of the solenoid. When the relay solenoids 310 and 3l5 are deenergized, no potential-is applied to the conductors 295 and 29-11 When the sole"- noid 310- of the increase relay 300 is energized;

currentflows from conductor 302 through blades 3I6and 3H and throughaconductor 318 to the conductor 297. The return circuit for the con trol phase of the motor 82 is from conductor 296 through blades 312 and'3-l'1 to conductor 303 Energizationof the solenoid 315 of the decrease relay 30! reverses the control phase of the motor 82. .In this condition, current from conductor 302'flows through blades 3| I and 3 I6, through conductor 3|9 to conductor 296, the return cir-- cuit being from conductor 291' through blades 3|! and 312- to the conductor 303 Selectiveen ergization ofthe solenoids 3 l'0and 3-1 Eds-possibleeither manually or automatically, as will'b'e hereinafter described.

tcmpcraturewontrol-circuit for operation of the heating unit 88' and the solenoid-operat-- ed valve 90 of the cooling unit 89 includes a transformer 3725 providing a primary winding connected between the conductors 302 and 303; and a secondary winding connected to conductors 326' and 32'! across which is connected a recep-- tacle 328 for the circuitsof the chrono-tachome-- ter system I28, I29. The conductor 326 extends toa solenoid 330 of a magnetic conta-ctor' 33!. When the'solenoid 330 i's energized, the contactor 33 i energizes the heating unit 88 by connecting it acrossconductors 333and 334con'nected across one phase of the output potential from the master control contactor 212. The remaining terable that the temperature be controlled to lie" between about 70 F. and 75 F. If SAE 50 oil is employed, the temperature giving'the desired viscosity will be between about F. and F. A double-throw, double-pole switch 338 is thrown to the left when the former oil is employed and to the right when the latter oil is employed Both blades of this switch are connectedto conductor 321;

The thermostatic switch means includes four thermostatic switches 340; 3, 342, and 343 submerged in the oil in the reservoir 81, or with thermostatic control units submerged in the oil. The switches 340 and 34| respectively close at 75" F. and 165 F., while the switches 34?. and 343' respectively open at 70 F. and 160 F. The first two switches are in' circuit with the solenoidoperat'ed valve 90 through conductors 344' and 305', while the'second two switches are in circuit with conductor 335;

The operation of the thermostatic switch meansis as follows. With the" switch 338 thrown to 'the'left and'with SAE'IO oil in the system at a temperature below F., current flows from conductor 321 through the upper blade of switch 338, the thermostatic switch 342, conductor 335, and through the solenoid 330, returning to the transformer 325 through conductor 326. This energizes the heating unit 88. When the temperature reaches 70 F., the thermostatic switch 342 opens this circuit and deenergizes the heater 88. Should the temperature rise to F. for any reason, such as continued operation of the test stand, the thermostatic switch 340 closes to complete a circuit from conductor 321 through the lower switch blade, the thermostatic switch 340, conductor 344, solenoid-operated valve 99, and conductor 345, the current returning through conductor to the transformer 325. This opens the solenoid-operated valve 99 and starts the flow of cooling liquid, which continues until the temperature drops below 75 F. With SAE 50 oil in the system and the switch 338 thrown to the right, circuits similarly traceable are completed through the thermostatic switches 34l and 343 to maintain the temperature between about F. and F. Temperatures of the oil in the reservoir are indicated by a conventional-type oil temperature gauge 348 on the control panel, while the level of the oil in the reservoir is indicated by a conventional gauge 349 on the control panel.

In the testing of electrical propeller governors or hydraulic governors employing electrical control equipment, such as the electric head previously described for adjusting the speed setting of the governor, various power sources, both A. C. and D. C., are desirable. The invention provides an electrical receptacle 359 for connection to electrical governor equipment through a plug 35| insertable into the receptacle. Connections T, U, and R are used for testing electric-type governors. As suggested within dotted line 353 associated with the plug 35!, the circuits within these electric governors are essentially a single-pole, double-throw switch operated by flyweights, the side contacts being connected to T and R and the intermediate contact, moved by the flyweights, being connected to U. Connections A, B, C. and D of the receptacle 350 are used for testing electric heads on hydraulic governors. Essentially. the electrical circuits within such electric heads are shown within dotted lines 354 associated with the plug 35!. The electric head includes a geared-down, series-connected electric motor which, in effect, adjusts the tension of the speech).- spring previously described. This motor has an armature 355 and field coils 356 and 351 adapted, when selectively energized, to rotate the armature in opposite directions. These field coils are connected through limit switches 358 and 339, normally in the position shown, to connections B and D, while the armature 355 is joined with connection A. When the limit of motion in either direction is reached, the limit switches 358 and 359 are selectively actuated to close the circuit from connections B or D (depending upon the limit switch which is actuated) through a conductor leading to connection C.

When testing such electrical equipment, there is need sometimes for l2-volt D. C. current and at other times for 24-v0lt D. C. current obtained selectively as follows. A transformer 365 provides a tapped primary winding connected between conductors 333 and 334, changing of taps being for voltage adjustment of two secondary windings 386 and and being made by turning knob 365:: (Figure 2). Bridge rectifiers 368 and 369 are connected respectively across the secondary windings, the output of each bridge rectifier being 12 volts. A three-pole, double-throw switch 310 is designed to deliver either 12-voit or 24-volt potentials to the equipment. The connections of this switch are conventional so far as concerns the outer blades and terminals. When thrown to the right, the output of rectifier 338 is connected across the supply leads 311' and 312. When the switch 31!] is thrown to the left, the rectifiers 368 and 369 are connected in series, through the outer blades of the switch, between these supply leads. The central blade of the switch is energized from the secondary winding of a transformer 313 through a conductor 314 to compl te circuits through signal lamps 315 and 316, as indicated, when the switch 310 is thrown respectively to the right or to the left. These signal lamps indicate to the operator whether 12-volt or Z l-volt potentials are being applied to the equipment.

The supply lead 31! includes a variable resistor 318 for minor adjustments of current or potential, this variable resistor being connected to a shunt 319 of an ammeter 388. Current from the far side of the shunt 319 flows through a conductor 38| to the movable blade of a single-pole, doublethrow toggle switch 384 which operates the motor of the electric head of the governor under test. Thus, when this switch is thrown upward, current flows through connection B to winding 356 and armature 355 in series, returning through connection A and thence through conductor 381 to voltage-changing switch 318. This operates the motor of the electric head in one direction until the limit switch 358 operates to open the motor circuit and close the circuit from connection B through the limit switch, conductor 369, connection C, and a conductor 389 to one terminal of a signal lamp 399-, the other terminal being connected to supply lead 312. Conversely, when the switch 384 is thrown downward, the motor of the electric head operates in a reverse direction until the limit switch 359 opens the motor circuit and completes the previously-defined circuit through the signal lamp 399. A signal lamp 391 is connected between ground and the supply lead 312. The illumination of this signal lamp indicates the presence of a grounded condition. A voltmeter 393 is connected between the leads 38l and 381 to indicate the voltage applied to the motor of the electric head.

A jack 394 receives a plug during testing of the double-acting governor and acts as a power source for the solenoid valve on such governor, this valve functioning to control the supply of oil for feathering. One terminal of the jack is connected to lead 381 through a conductor 395. The other jack terminal is connected through a double-pole, single-throw, blade-connected switch 396, to the conductor 38! through a conductor 391. The lower blade energizes a signal lamp 398 connected to the supply lead 312. Similarly, a jack tilt] receives a plug extending to the cut-out switch on the feathering control of a hydraulictype governor, which cut-out switch is conventionally mounted on the side of the governor. The jack 460 is energized through a switch 40l in series with a signal lamp 492 and the conductor 314 extending to the transformer 313, the circuit being completed through ground.

To provide for manual and automatic control of the speed of the governor during test and to provide for the selective testing of diiTerent-type governors, the invention employs a selector nspe v y f r mmualafleat g ele tr sype ov rnors,lmdqt gine s e @tions; 3 v and; 4 are respectively to and automati ope ati nof liydiiaul wtyp Q m re -un r o fite taa d; a mp yedwf ffi d t ma ah i ccumu at ii an ide ib .insfi o er o prwici s Y1.i 7 Pos t ons iandfia e res ctively for m ime ie treme positions.

r. a d; 4 fta Siandncont cti vibe ,M

r switchJHll. ,I'his selector switch risp reffirfilbly of the rotary type and provides four, banks i; switch io op automat c o e tion ofth S layl rail q overn -.known as ,controllabl fi or co s ant s eed ov- ,,e1'nors, such aspreviouslyI mentioned andi which are undergoing test.

v 1On bank Lecontacts I; 3,;and5 areielectrieally common, as shown,,-, andare connected-by a con- .ducton M5 to anloweracontact of an-fifincrease" pallet switch ,4] 6, the. pallet normally 1-closingathe v. upper contacts as shownrbut being manually; de-

. pressible to close the-lowercontacts. Similarly, ontbank D, contacts I',: 3, ande5:.arenelectrically common andiareuconnectedi by. alconductoiz lll with-one of the lowertcontactshoft a iidecrease pallet switch M8,.this, pallet normally closing the upper contacts as shown but being manually depressible to close the lower contacts. Qne-hf the upper contacts of each of the switchesdifi and 418 is connected by a conductor illfi tothe intermediate contacts 45'! and-4511 -ofthe 'a-utomatic controlunit 33 and to the secondarywinding of v a a transformer 422, the primary "of; which is con nectecl between conductors-fwlandfiflflm ifhe remaining terminal of this secondary winding is connected by conductor i24 to- 1imit' switches 425 and liifi of the pilotmotor 82, these switches being of the conventionaltype and being respectively openedwhen;the control shaft 137 of the va riahie-speedtransmission 9!- reaches desired ex- These limit switches serve merely to deenergize the pilot motor 82 toprevent its continuing the oneration of the control-shaft i3"! beyond the operating limits of the variablespeed transmission, The limit switch lis connected to one terminal ofthe solenoid 31,0 'ofthe increase relay -3El0 through conductor lzl gimilarly, limit switch 425 is connectedthrough con- :ductor 428 to the solenoid3i5 of the decrease relay L The remaining terminal of the solenoid 3!!! is connected by conductor; 4 3 0 to the blade of hankl. Theremaining termjnal of the l noi 3'5 is eenn t d ye onduetor ct blade of bank D.

na 2 1 bank and, .conte if 2 of nk. a e elec rica lveonnet edb conductor M r o nec nc' f of .re eptaclw he kD a con act le d. ban fiii on r onnect by v a? cqndlwli ra I ne ti nfi h sr lisa ac -fie m ie U co nec hmus fl l wfi lfi' V W4? ac is e inatei e ren iqmerA -L saws l8 interconnected: and ,extend to .idecreasev c orit o t au omat q o t lueii ,8 htone a conductor ,{i44. Contacts 5 and}; oi bank S1 and contact tof bank D are electrically joined L andconnectedhy a conductor M5 to f decrease contact 169' oi'the automatic control unit. Cont acts, and i. of bank Sz and contact-lot bank I are electrically common and r are connected th ough a conductorfififi to increasef contac, t.I10 10 01" he automatic control unit. Contaots 5 and 6 re Pa-11 t $2. n n a t 9 of b nk I, a elec r; ocal y c mm n n a con e ted thro h, (Q rduotor its? to fincrease contact ,lfiilf of the aul .tqmatit tcont lll A simple indicator,circuitis employed toim d1 teselective ,energization of fsoleno id 3jil of 1 e increase reiay and solenoid 315 of the dehcreaselrelay. Thus, the blade 01fv banhs isconnected through a conductor 450 through, signal zufllamll. 4 5L120 conductor @334 to be in paralleli with .it els n iitfi eft de rea e e a Thab t of bank S2 is connected through aconductor, 452 ipl'asignal lamp :iEZito the conductor 42d to be v in parallel with thesolenoid 3m oi the inc ease zsrre e A, ro nd-indi atin S tna ,lemnh4., is .(.,c9nnecte ci between a ground on the frame of the Jest- Stand and theconductor fl'ld. Itsilluminm tiqnind e tesa eround d w dit n in th equ ment beingtestedand which, except when 7 test- 30 the .t c en d o a doub ti eo ern ere a groundshould he indicated, should be v inf st d-l e o e ceedin w h. t e. t

iqmrc on f, a mat c. co tr ea The operation of the automatic control means will be exemplified with reference to the type of governor shown in Figures 13 and 14. Assuming -thatqthis governor has been connected to; the

pad llll'i and that oil, at subst antially engine ac pr ssur is being supplied-theret through pipe I I from the low-pressure pump-94,'it will be evident that an overspeed condition will raise the-pilot valve 55 to discharge high-pressure oil from the governor pump to through pipes "I- I3 and 206 to the inboard chamber 205 ofgth'e hydraulic actuator 84. This moves the piston 209'1eftward, aslyiewed in Figure 10. Oil from the outboard chamber zct 'is expelled through the pipe-103 through now-open valve;22l l into'the pipe 11 l in which the pressure is regulated to simulate norj mal engine pressure.

Leftward movement of the piston; -20uturns'the gear; l flil ;cl ockwise (viewed downwardly) thus turning both control drums 16s and 1 60 counterclockwise. This brings-the fdecrease contact I6 3 into elect1fic engagement with the intermediate contact I51 carried by the controldrum I50. iThe selector switch 410,1 having previously been set at position 4 (corresponding to automatic operation for this type of governor), a circuit jis gompleted from the transformer A22 through the; conductor 42 61 intermediate contact"! 51, de-

: creasef contact {69, and through conductor- 444 ,to contact 4 of bank D of the selector switch,

65 j the current then flowing through the blade ofthis bankthr0ugh conductor 43! to the solenoid-3l5 "of the decrease re lay, thence throughlthe conductor-li28, limit switch 425, and .conducton-lfl l ttolthatransfOrmer. Thiscloses the contacts of 7.-.;-the-.idecrease relayand causes the pile motor emi-to revol e the c nt io sh s fil fa ev riab ela sed un t saun r-c wi re lieet r d cing tl'ie,speed; of the governor. con nicerc wise rotation of the control shaft 1 3?! moves 19 until the intermediate contact I51 separates from the decrease contact I89, whereupon the pilot motor 82 is deenergized. The momentum of the pilot motor is suihcient to bring the intermediate contact I51 substantially to its centralized position between the contacts I69 and I10.

A very slight leftward movement of the piston of the hydraulic actuator will cause substantial movement of the lower control drum I60 due to the step-up gear ratio between the gear I80 and the pinion I14. In fact, the decrease contact I59 moves sufficiently not only to touch the intermediate contact E51 but to displace it and cause it to follow the movement of the decrease contact IE9 until the piston 280 stops its leftward movement, i. e., when the governor reaches an onspeed condition to close its pilot valve 55. This bodily movement of the intermediate contact I51 to a new position is readily understandable when it is remembered that the upper control drum I5 3 is frictionally coupled to the shaft I48 through frictional engagement with the surface I19 of the gear I68 when pressed thereagainst by the spring H8. The lower control drum I60, on the other hand, is free to rotate on the shaft IE6 but is positively geared to the oscillating shaft iSI which partakes of the motion of the hydraulic actuator SL1 so as to be solely dependent upon the hydraulic actuator for its rotation. So long as the overspeed condition exists, the decrease contact 239 is thus moving the intermediate contact It? counter-clockwise and the rate of counter-clockwise turning of the shaft Hit or the control shaft I3? is insufficient to break the contact during such movement.

However, as soon as the pilot valve of the governor closes (representing an onspeed condition), the intermediate contact IE1 is drawn away from the decrease contact I69 to interrupt the circuit to the pilot motor 82, as described, and the momentum of the pilot motor 82, as described, and the momentum of the pilot motor moves the intermediate contact I51 to a new, approximately-central position between the contacts I69 and I'lil.

An underspeed condition of the governor lowers the pilot valve a5 and permits rightward movement of the piston 26% or" the hydraulic actuator under the influence of engine-pressure oil from pipe IlI through pipe 283. from inboard chamber 255 through the pipe 206 and pipe l 53, thence through the now-open pilot valve 55 and into the chamber I92 of the pad I00 to drain through the pipe H1, flow meter 250, and pipe 25I to the reservoir 81.

The resulting rightward movement of the piston 20E] turns the lower control drum I clockwise to bring the increase contact [18 into pressural and advancing relationship with the intermediate contact I53 to energize the solenoid 3H1 of the increase relay as follows. Current from the transformer 422 flows through conductor 420, contacts I51 and I18, and conductor 446 through bank I of the selector switch, conductor 430, solenoid 3H3 of the increase relay, conductor 421, limit switch 425, and conductor 424. This energizes the pilot motor 82 to revolve the control shaft I31 clockwise, i. e., in a direction increasing the speed of the governor. When the governor reaches an onspeed condition, the motion of the piston 29!) stops, the intermediate contact I51 separates from the increase contact I10 to break the circuit, and the pilot motor 82 coasts sufficiently to substantially centralize the 20 intermediate contact I51 with respect to the contacts I59 and I10.

So long as the governor remains in an onspeed condition, there is no movement of the piston 200 sufiicient to close either energizing circuit of the pilot motor 82, whereby the driven speed of the governor remains as determined by the automatic control.

When testing controllable governors, compensation must be made for the opposed hydraulic relationships as compared with the Hydromatic governor. When the controllable governor is in overspeed condition, the pilot valve in the governor releases oil from the inboard chamber 2535, allowing the oil pressure in the outboard chamber 262 to force the piston 293 rightward. This revolves the gear I88 counter-clockwise and the control drum I621 clockwise. This action brings decrease contact I69 against the intermediate contact I51 to energize the decrease relay. This causes the pilot motor to revolve the control shaft I31 clockwise to reduce the speed of the governor. It also turns the control unit I59 clockwise to interrupt the circuit when an onspeed condition is obtained.

When such a controllable governor is operating in an underspeed condition, the pilot valve within the governor allows high-pressure oil to enter the inboard chamber 285, forcing oil from the outboard chamber 232 and moving the piston 2GB leftward. This action revolves the control unit I80 counter-clockwise, bringing the increase contact I18 into engagement with the intermediate contact I51. This causes the pilot motor to increase the speed until the pilot motor circuit is interrupted by counterclockwise rotation of the control unit I53.

Typical test procedures In testing all of the above-mentioned types of hydraulic governors, the governor is properly mounted on the pad I05 and the apparatus started under conditions for manual control, as follows. Valves 2I9, 232, and 244 are opened, all other valves being closed. Selector switch M0 is turned to the manual position corresponding to the hydraulic-type governor being tested, 1. e., at positions 3 or Master start switch .215 closed momentarily to energize the system, and

the pump is started by momentarily closing Oil is displaced start switch 292 after the oil has been brought to the correct temperature by closing the switch Thereafter, either for-yard switch 236 or reverse switch 281 is momentarily closed, depending upon whether the rotation of the governor being tested is clockwise or counter-clockwise. The governor will now be rotated by the drive unit at a speed determined by the setting of the variable-speed transmission. Low-pressure oil will be supplied to the overnor through the pipe HI and the oil pressure in the pipe II3 wil1 cause a small now through the fixed orifice 243, if valve 244 is open, to duplicat transferring leakage.

To test the low stop setting of the governor while employing manual control, the control pulley 61 of the governor is turned to low R. P. M. position. Decrease switch MS is then depressed to energize th decrease relay and rotate the pilot motor in a direction to decrease the speed of the governor. Assuming for the moment that the Hydromatic governor of Figures 13 and 14 is being tested, the selector switch then being at position 3, the governor is operating in an overspeed condition and two circuits are closed as follows: An energizing circuit for the pilot moi e ieaess 21 i tor 82 is completed from ithe" transformer I 422 through conductorAZU, closed upper contacts of increas'e switch 416, now-closed lower contacts of decrease switch 410,- conductor 41?, bani; D of the selector switch. conductor-43 I, solenoid 3i 5 of decreaserelay 30I, and thence through the limit switch 426 and conductor 424 to thetransformer. A signal circuit is also completed from the'conductor 420, intermediate contact I51, de-

lcrease contact I69, 1conductor4 l4, bank S1 of 'the selector switch, conductor-450, signal lamp 45l, and conductor 424. Energization of the decrease relay 30I reduces" the driving speed so long as the decrease switch 418 is depressed. Howeven when the governor speed reaches the low stop setting, the pilot'valve' of the governor closes, evidencing an onspeed. condition which stopsithe'operation of the hydraulic actuator and, as'previously described, breaks the engagement 'between the intermediate contactv I51 and the.

decrease contact I69. In manual operation, this merely deenergizes the signal lamp 45 I. The pilot motor will tend to continue its rotation until stopped by opening of the limit switch 426 or the decrease switch 4I8. 'Whenoperating the;

' system by manual control, it is usually impossible to}st0p= the pilot .motor byireleasing the switch Bat the exact instant an onspeed condition is achieved. Rather, the switch 4I8 is held closed until the signallampz45lgoes out and signal lamp 453immediately illuminates through a circuit including the intermediate'contact I51, increase contact I10, and. bank S2 of the selector switch. By then. alternately and momentarily closing increase switch M6. and decrease switch 4| 8, the operator will be able to extinguish both signal lamps 451 .and 453,1at which time .the governor is rotating inonspeedcondition and the low R. P. M. reading may be observed from the tachometer I21 and checked more accurately ronxthacounter I28: and timer I29 of the chronoita-chometer system.

lWhenwtestingthe/high stop setting of the ;.governor :while employing .manual control, the

-.control;.pulley 01 of the governor is turned to ahigh P. M.-position-.against itsstop and in- :crease.;and decrease -'switches M6 and M8 are zactuated until bothsignal lamps 45I and 453 ex- .tinguishindicating an onspeed condition of the :governor. Again; the high R. P. M; reading may :be taken from the tachometer and checked with ..=the counter. and timer.

,Usu'ally; such tests: for setting of the low stop sand-thigh stop of the governor are made with the Jsystem' set .for automatic. operation, thus eliminatuing any necessity for manipulation. of the in- ;crease and decrease switches 44% and M8. To -do;this,.the selector switch M0 is turned to the f automatic position corresponding to the goverinort being tested, e. g., at point'4 for a Hydro- .smatic'governor. Thecontacts in the automatic control unit 83 then become operative to bring the,.-governor promptly and automaticallyto an oonspeedcondition at the low stop and highstop settingsuas will.be apparent from the previous -.descr,iption as to the operation of the automatic control means. It is usually preferable always to istart the test stand when set for. manual operantion-and .then to turn: the selector switch to the corresponding automatic: position.

iWhen testing. double-acting governors in'the .iabovetests; valves 220 and 244 should be closed sand valve 2255 opened. .This connects the out- -:board'. chamberiofthe hydraulic: actuator 84 with ithenoutboard output.:passage II4':of.the'pad. I00

/ through: pipes I li and 204; this type otigovernor thus controlling the pressure:inithe outboard chamber as well as-inthe' inboard chamber, the latter control being through'zpipes I 'I 3.: and f206, as previously" mentioned.

In making recovery tests onall hydraulic governors, the test-Standis setifor manual operation and increase and decreaseswitches llfi. and M8 are operated to bringithespeed=ofithe governor to one of the limits or the recovery-test; conventionally 2000'-R. P. Thecontrol pull'ey 61 of the governorvis then turneduntils signal lamps 45I and 453. are zex'tinguished, indicating that the governor is onspeed; the location: of the control pulley being suitably marked. By switches M0 and M8, the-*speedobthe. governor.is"then brought to the other limit for the test; conventionally 2400 R. P; Ma andfithe'governor tcontrol pulley 61 rotated until the same signal lampstare extinguished; indicating an onspeed condition; the location of the control .pulleybeing again marked. The selector switch 4 l0 'isithen '.turned to the automatic position corresponding to the governor under test, and the valve 232 is opened. This places the system in automatic operation.J1'Ihe control pulley is then moved' from its latterposition (2400 R. P. M.) to the marked .formerz-position (2000 R. P. M.) I quickly;'- while at the same instant starting the timer l I 29 I by :pressing: the start button I30. The -automatic -operation. reduces the speedandthasignal lamps 45 Iu-and453 will alternately come -on fnear 'the onspeed condition as the governor conditions stabilize. At the instant both signal-lamps are'extinguished, the button I30 is again -pressed,..thus stopping the timer. The intervening-time. should: not exceed a standardized figure, usually" 15=seconds, if: the recovery of the: governor-is to 'be'satisfactory. Further, the governor shouldwnot pass the setting more than four times,nas indicated by the-signals of lamps 45I and453. 'I hel foregoing procedure is then repeated, with the setting beingssuddenly reversed from :the lower speed (e. .g., F 2000 R. P. M.) to the .higherspeed .(e.'g.,.2400 R. P. M.).

Propeller governors are :usually *counterbalanced so that, if the cable to. the speedcontrol pulley breaksthe governor will automatically change the pitch of the blades to that desired for cruising or some other predetermined "flight condition. The counterbalance spring 10a at the extreme upper end of Figure 14, opposing the speeder spring 10, serves in this capacity. The counterbalance R. P. is a usually checked" from low speed position and from high speedposition. In the former and with-the system adjustedior automatic control, the controlpulley 61 is turned toward low R. P; M. position unti-lthe: governor automatically controlsand-operatesat about 1500 R. P. M., whereupon the=.control :pulleywisireleased from manual.zengagement. It. will then move slightly one wayor the. other and. stop. When signal lampsi45l;.and 453 are extinguished, indicating an onspeedcondition, the counterbalance R. P. M. can beread from the tachometer I217. When tested from. high: speed :position,: the pulley is turned until thergovernor operates :at approximately 2500 R. ;'P.I M., "being then; re leased and the counterbalanceR- P.*M.xbeing read from the tachometer whentthesignallamps 45I and 453 are extinguished.

The above tests apply toflallzof -the hydraulictype governors. 'Theifo'llowing additional tests can be made onHydr.omaJtic: and fcontrollable governors.

In testing the capacityoofx thezgovernorzpump,

the test stand is adjusted for "manual operation and the control pulley of the governor is turned to low R. P. M. position. The governor speed is then brought to about 1750 R. P. M. operating switches H6 and M8. At this time, oil is being delivered to the governor through pipe I l l and discharged from the governor pump through the pipe l l3. Valve 232 being closed, the flow is through the valve 23? to the reseroir 5'3 through the flow meter 2:20. The valve controls the back pressure against the pump and adjusted until this pressure, read on the pressure gauge 235, is 150 lbs/sq. in. The capacity of the governor is then read on the meter connected to the flow meter 230. This capac y must be Within limits specified for the particular governor.

The relief pressure test is to determine the pressure at which the .iei valve of t -e governor opens and is usually performed when the governor is runn ng at 1150 R. P. M1, the control pulley being in mi hum position to insure operation of the gov; ior in overspeed con dition. The valve 23? is now completely closed and the governor pressure, determined by the pressure relief valve 85, is read from the pi"=ssure gauge 235.

subjected to high pressure. Valve is cle and valve 22? is opened to deliver oil from high-pressure line 2'23 to the pipe ill, the ta. c 2|9 being closed. This transfers high-press oil to the pipe ill. The valve 22? adjust" until the pressure gauge 235 reads 400 lbs/sq At this pressure, there should be no eXte leakage {or approximately one minute. if external leakage pressure is the as relief sure, valve 22? need not be used and the external leakage test can be conducted withoument of auxiliary pressure irom the higlnpressuro line 223.

The internal leakage test deteri leakages of the governor. In making this the valve 23? is adjusted so that predete pressure is applied to the governor, usuall the pressure gauge indicates 150 206 its J. in. Leakage will be through the pipe it? flow meter 250, the latter is ing readable to determine the leakage rate and, correspondingly, the condition of the valves, etc, within the gove:=:- nor.

Feathering tests are made by connecting 1 flexible hose Hi) to the high-pressure port of the governor. The test stand is st ed in manual control and the governor pr y turned to bring the speed to approximately 2. R. P. M. by operation of switches and Valve 220 is closed at this time so that the on of the high-pressure pump, controlled pressure regulator 222, is delivered to the valve 228. This valve 228 is then opened until the sure, indicated on the gauge is suficl open the feathering or high-pressure va the governor. When this valve opens, there be an increased fiow through pipes H3 nd. which can be noted on the meter 2 3i CO1 to the capacity flow meter 2 In checking the cut-out sviit .1

in the feathering control, the cut-out switch connection the governor being placed onspeed by operation of switches H6 and H8, previously described. The switch. 40! is closed to send current to the cut-out switch on the governor and this will illuminate the signal lamp 402. VIit-h the valve 225 closed, valve 228 is opened and valve is slowly closed until the pressure on the gauge 235 reads approximately 500-600 lbs/sq. according to the type of cut-out switch being tested. When the cut-out switch opens, the signal lamp goes out and the pressure at this instant can read on the gauge 235. Valve ZS-l? is then slot. opened and, when the signal lamp illuminates, showing that the cut-out switch has age. 1 closed, the pressure can be read on the gauge 235.

In testing high-pressure accumr type governors, the capacity test, pressure relief test, external leakage test, and internal leakage test are made substantially as above, with the governor operating at a back pressure of about 15b lbs/sq. in. and at a supply press .re of 43 plus or minus 15 lbs/sq. in., the governor speed beig adjusted to 1750 R. P. M. by use of sv hes ilii and The opening and closingpressure of the accumulator shut-off valve of such a governor can be tested by connecting the high-pressure hose its to the accumulator port and turning the control pulley of the governor to minimu 'l position. The valve 23! is closed and the relief pressure of the accumulator shut-01f valve can be read. from the pressure gauge 235. Valve is then closed until the gauge reads 230-300 lbs/sq. in., or as otherwise specified. When the shut-off valve opens, the gauge 3?: will show a rise in pressure. Valve 228 is then slowly opened until the gauge reads 50-240 lbs/sq. in., or as otherwise specified for the test When the shut-off valve closes, the gauge w read a drop in pressure, the ;ressure just before the drop being the closing pressure.

In testing double-acting governors, valves 232, 228, and 244 are closed. The capacity test is made at a back pressure of lbs/sq. in. and a supply pressure of 40 plus or minus 15 lbs/sq. in. With the governor running at overspeed condition, the valve 23! is adjusted so that the gauge 235 reads approximately 150 lbs/sq. in., whereupon the pump capacity is read on the meter 24 l. The pressure relief test is made under similar conditions, except that the valve 237 is completely closed, whereupon relief pressure can be read from gauge 235. The control pulley of the governor is then turned to maximum R. P. M. position and the governor speed adjusted to 1750 R. P. M. so that the governor is operating at an under-speed condition. The valve 256 is then completely closed and relief pressures are read on the gauge 255. The external leakage test is made with the governor operating in overspeed condition, as mentioned above. The valve 231 is completely closed and the valve 221 opened until the pressure gauge 2l8 reads the required pressure. Operating for approximately one minute, there should be no external leakage. Similarly, the internal leakage test is made with the governor in the same overspeed condition, the valve 231 being adjusted until pressure gauge 235 reads 150-200 lbs/sq. in., while gauge 2|8 should read 40 plus or minus 15 lbs/sq. in. Internal leakage is indicated on floW meter 250.

The relief back-up selector Valve of a doubleacting governor can be tested by connecting the flexible hose H9 to the high-pressure port and turning the control pulley to minimum speed position. Valve 23'! is closed and the pressure gauge 25, 235t shouldx'read, 150-200 lbs/sq; in. Valve 228 is opened untilpressure gauge 23!] .read 40-50 lbsz/sq. in;- If the pressure indicated by thegauge 235. rises, the'relief back-up selector. valve is shifted. The maximum'pressure required to shift thisrvalve should be 50-lbs./sq. in. Leakage of the ssolenoid feathering-valve can bedetermined by. stopping the'governor, opening the valve 228 until a pressure of 100 lbs/sq. in. is indicated on the gauge 230. Internal leakage can be measured by the flow meter 25!), the solenoid being deenergized.

In making the feathering test on a doubleacting governor; the governor is not rotated and oil under pressure is supplied to the feathering connection. Switch 396 isclosed to-energize this.

solenoidtocheck the operationof the feathering port vcheck valveand the solenoid valve. The former should open when oil at about 250 lbs/sq.

in..is supplied. Under this condition, oil will flow through the pipe H3 :and valve 231 is closed so that the pressure is indicated on the gauge'235. When the solenoid is deenergized by opening the switch 396 and the pressure relieved below 150 lbs./sq. in., the solenoid valve should close to permit no flow to the pipe I I3. Unitsequipped with cut-.outswitches can alsobe checked for sWitch opening pressure.

Electric-typengovernors are commonly divided into two types, known-as:proportional governors and lubricated'pad governors. Basically, such governors control .areversible pitch-changing electric motorthrough a single-pole, doublethrow switch, the intermediate contact being moved in response to flyweight position. In most proportional governors, this movement is effectedby use of an oil servo mechanism supplied with governor-pump-pressured engine oil under control of a pilot valve operated by the flyweights. While the proportional governors are not illustrated in the present specification, the following generalized I description will be understood by those skilled in thetesting thereof and will suggest, also, tests. which canr'be made by the present invention. on .lubricatedpad governors.

In testing such proportional governors, oil is supplied to theline I H at a low pressure of 2-3 lbs/sqin. (read on-gauge 2H3) by opening valve 2l9- suiiicient to accomplish this. To adjust the valve ofesuch governors, they-should first be operatedat about 2000 R; P; M., after which the quadrant lever should be moved from high R..P.. M.. to low R. .P. M. position. The pressures obtainedinthe servo cylinder must vary from less thant5 togreaterthan 75 lbs/sq. in and will be 5' indicated by installation of the inspectors test pressure gauge on the'governor. If the minimum pressure is not-obtained, shims are'removed; if

maximum pressure. is not obtained, shims are added... The double contacts of the governor should be adjusted so .that an oil pressure in the servo cylinder of 1042 lbs/sq. in. will give the full indicationon the correct R. P. M. contact. Ifthe .oil pressure is greater than 12 lbs/sq. in.,

shims are removed from. the double contact. If

and .decrease relays 300 and-3e I are respectively controlled by thesidecontacts connected to T and Thus, automatic R, respectively. In effect, the single-pole, doub1ethrowswitchof the governor performs a function.

performed by the automatic control unit 83 when testing automatically hydraulic governors, At any setting of the governor, any offspeed conditionswillquickly'be corrected by change in drive speed and thecontrol arm of the governor can.

be moved to any selected position and the governor drivingspeed will automatically changeto v permit testing of actual speed of different settings.

at a series of different speeds.

different speeds.

45f and 453. decrease lamp 45! lights continuously.

the high R. P, M. range. The low R. P. M.

range is obtained by bringing the governor .to onspeed condition, decreasing the speed untilfiine v crease lamp 453 lights continuously, and 1711611.;

The neutral zone is, obtainedias follows. Bring governor into onspeed: condition, increase speed until decrease lamp. 45!.lights, then decrease speed until lamp 451- subtracting the speeds.

darkens. Thedifference between the finalR; vP. M; and the onspeed R. P. M. is the neutral zone! The same test is repeated by bringing thegovernor toonspeed condition, decreasing speed until... increase? lamp453 lights and increasing speed:

until this lamp darkens, the differencebetween.

the last speed. and the onspeed condition giving.

the neutral zone.

The take-off setting ofthe electric governor is adjusted by holding the control leverragainst. its stop pin :and adjusting the stop. setting to bring -.toi-correct speed, i. e., when both.- lamps.

45! and 453 are extinguished. Also, the low- R..P-. stop settings can be similarly adjusted on electric-governors provided with remote @con-.--

trol type head.

Such governors often employ a hydraulic safety switch which opens if the oil pressure fails. To

testthis, thecontrol lever is set at take-off? position: and the governor is driven overspeedby 10'or 15 RP. M. The oil supply to the governor is then stopped, as by closing valve2l9 to open. thesafetyswitch. There should be no increase. R. P; M. correction if the switch is operatingproperly.

Various changes and modifications can be made: without departing from the spirit of the invention.

as defined inthe appended claims.

I claimas my invention:

1. Inanapparatus for testing electric propeller governors having switch means for selectively a gOV- ernor' mounting means; means for detachably connecting said governor to said governor mountingmeans; drive means for driving said governor closing two circuits, the combination of when mounted on said mounting means; a: pilot motor and means for connecting said pilot motor. tosaid drive-means to increase and decreasethe speedof said governor in response to forward and rearward actuation of said pilot motor; control circuits for said pilot motor and adapted when respectively energized to actuate said-pilot motor in:.forward' and reverse directions; and" means for electrically connecting said switch-v means of said governor tosaid control circuits. 

